1. Field of the Invention
The present invention relates to an electronic throttle control apparatus including a throttle opening degree feedback control means for feedback control of a throttle valve by using an opening degree position detected by a throttle opening degree sensor.
2. Description of the Related Art
An electronic throttle control apparatus including a throttle opening degree sensor, a throttle actuator having a motor, a target opening degree position setting means, and a throttle opening degree feedback control means is conventionally known (for example, see Japanese Patent No. 3713998; hereinafter, referred to as Patent Document 1). In the electronic throttle control apparatus described in Patent Document 1, the throttle opening degree sensor detects an opening degree position of a throttle valve which is closed and opened to adjust an amount of intake air sucked into an engine. The throttle actuator opens and closes the throttle valve by energization of the motor. The target opening degree position setting means sets a target opening degree position of the throttle valve in response to a signal output from a control means of the engine. The throttle opening degree feedback control means receives an input of the opening degree position from the throttle opening degree sensor and an input of the target opening degree position from the target opening degree position setting means and performs feedback control on the throttle valve to match the opening degree position and the target opening degree position with each other.
In the case of the disclosed electronic throttle control apparatus, for the engine start, after a current larger than a reference value is made to flow through the motor for a predetermined period of time to place the throttle valve in a full-close position, a value of the current made to flow through the motor is reduced to be smaller than the reference value to turn the throttle valve from the full-close position toward the opening side by a predetermined opening degree. In this manner, an overcurrent is prevented from flowing through the motor, while the size of particles of a fuel is reduced to improve fuel efficiency.
In the above-mentioned conventional electronic throttle control apparatus, however, the current flowing through the motor and the opening degree position of the throttle valve have a hysteresis relation. Therefore, even when the throttle valve is at the same opening degree position, the current required for the motor differs for each driving direction.
As a result, it is still difficult to turn the throttle valve from the full-close position toward the opening side by a predetermined opening degree to place the throttle valve in a desired opening degree position only by performing open-loop control to make the current flowing through the motor smaller than the reference value.